Fractures commonly occur in the femur, and especially in the femoral neck and intertrochanteric regions. Traditionally, these fractures have been treated using a nail located in the fernoral head in cooperation with a side plate located on the outside of the femur, or in cooperation with an intramedullary nail located in the intramedullary canal. The nail cooperates with the side plate or intramedullary nail to align and compress the bone fragments.
A high incidence of death is associated with hip fractures due to the injury itself or related complications. Frequent complications may arise when two or more bone fragments are forced towards each other when the patient supports his or her weight on the healing bone. For example, a sharp implanted nail or hip screw may cut through and penetrate the femoral head or neck; or a nail, hip, screw, side plate, or intramedullary nail may bend or break under load where the contact between bone fragments is insufficient for the bone itself to carry the patient's weight.
A variety of compressible fixation systems have been developed to maximize bone to bone contact while permitting bone fragments to migrate towards one another. For example, helical blades have been developed that may be inserted into and secured to the neck of a femur, and coupling mechanisms have been developed to slidably couple the helical blade to a side plate or intramedullary nail.
The prior art blades, however, may be susceptible to migration within the bone fragment and, even worse, may break free or pull out of the bone fragments, thus allowing the bone fragments to separate and/or become misaligned. Prior art blades are also susceptible to bending stresses, which may lead to undesirable bending or breakage of the blade.
In addition, many prior art coupling mechanisms provide unlimited amounts of sliding between the blade and the side plate or intramedullary nail, which may lead to disassembly of the blade and side plate/intramedullary nail. Furthermore, prior art coupling mechanism are often complicated and difficult to assemble during implantation.
Thus, a need exists for improved bone fixation systems.